add monitor.LogOnce method

docs/release-notes.md

@@ -12,7 +12,8 @@
 * For modders:
   * Added support for flipped and rotated map tiles (in collaboration with Platonymous).
   * Added support for `.tmx` maps using zlib compression (thanks to Platonymous!).
-  * Mods are no longer prevented from suppressing key presses in the chatbox. Use this power wisely.
+  * Added `this.Monitor.LogOnce` method.
+  * Mods are no longer prevented from suppressing key presses in the chatbox.
 
 * For the web UI:
   * Added option to upload files using a file picker.

src/SMAPI/Framework/Monitor.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using StardewModdingAPI.Framework.Logging;
 using StardewModdingAPI.Internal.ConsoleWriting;
@@ -26,6 +27,9 @@ namespace StardewModdingAPI.Framework
         /// <summary>The maximum length of the <see cref="LogLevel"/> values.</summary>
         private static readonly int MaxLevelLength = (from level in Enum.GetValues(typeof(LogLevel)).Cast<LogLevel>() select level.ToString().Length).Max();
 
+        /// <summary>A cache of messages that should only be logged once.</summary>
+        private readonly HashSet<string> LogOnceCache = new HashSet<string>();
+
 
         /*********
         ** Accessors
@@ -74,6 +78,15 @@ namespace StardewModdingAPI.Framework
             this.LogImpl(this.Source, message, (ConsoleLogLevel)level);
         }
 
+        /// <summary>Log a message for the player or developer, but only if it hasn't already been logged since the last game launch.</summary>
+        /// <param name="message">The message to log.</param>
+        /// <param name="level">The log severity level.</param>
+        public void LogOnce(string message, LogLevel level = LogLevel.Trace)
+        {
+            if (this.LogOnceCache.Add($"{message}|{level}"))
+                this.LogImpl(this.Source, message, (ConsoleLogLevel)level);
+        }
+
         /// <summary>Log a message that only appears when <see cref="IMonitor.IsVerbose"/> is enabled.</summary>
         /// <param name="message">The message to log.</param>
         public void VerboseLog(string message)

src/SMAPI/IMonitor.cs

@@ -18,6 +18,11 @@ namespace StardewModdingAPI
         /// <param name="level">The log severity level.</param>
         void Log(string message, LogLevel level = LogLevel.Trace);
 
+        /// <summary>Log a message for the player or developer, but only if it hasn't already been logged since the last game launch.</summary>
+        /// <param name="message">The message to log.</param>
+        /// <param name="level">The log severity level.</param>
+        void LogOnce(string message, LogLevel level = LogLevel.Trace);
+
         /// <summary>Log a message that only appears when <see cref="IsVerbose"/> is enabled.</summary>
         /// <param name="message">The message to log.</param>
         void VerboseLog(string message);